Iii Core Primitives

This is the foundational layer for building workers and wiring up functions in iii. You'll use it when registering local handlers or wrapping external HTTP endpoints, binding triggers like cron or pubsub to those functions, and choosing whether to call things synchronously, fire and forget, or enqueue for reliable processing. The primitives are consistent across TypeScript, Python, and Rust, with the same double-colon naming for function IDs and the same trigger shapes. Most developers will interact with this once when scaffolding a worker, then rely on higher-level capability workers from the registry for databases, queues, and observability. If you're authoring custom trigger types or need fine-grained control over invocation modes, this is where you'll spend time.

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last updated: Aug 21, 2026

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Install

$ npx -y skills add iii-hq/iii --skill iii-core-primitives --agent claude-code

Installs into .claude/skills of the current project.

Files

Core Primitives

iii has three primitives:

Worker: a process that connects to the engine, registers functions, and calls them
Function: a named unit of work such as orders::validate; any worker runs it with call
Observer: iii.observe(a, b): when a runs, b runs

Everything is reactive. An HTTP request, a cron tick, a queue message, and a state change are each a call of a source function (http::on-request, cron::on-tick, queue::on-message, state::on-changed), so observing that function is how work starts on the event. See iii-observe.

Use :: in function IDs, leading slashes in HTTP path args, and expression for cron args.

Function Registration

Register local handlers when you control the implementation. To call an existing external endpoint, register a handler that makes the HTTP call. HTTP-invoked functions (HttpInvocationConfig, iii-http-functions) are deprecated and will be removed in an upcoming release.

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Details

Repository: github.com/iii-hq/iii
Categories: Backend & APIs, Python, Rust
First seen: Jul 14, 2026